Vibrations caused by operating jet engines on an aircraft have a detrimental effect on both the performance of the jet engine and the comfort of those aboard the aircraft. Jet engines, particularly turbofan engines, contain a number of components which rotate about a central axis. Because vibrations can introduce eccentricity in the rotation, vibrations can degrade the performance of the engine. The reduced performance can be manifest as a decrease in thrust, which can, in turn, increase the length of a flight as well as the fuel required. The vibrations also can travel through the frame of the aircraft to compartments containing passengers and operators. While not harmful, vibrations can be an unpleasant aspect of travel for the occupants.
The most common approach to reducing the impact of vibrations on rotating turbomachinery components is to provide a squeeze film damper (SFD). Typically, a bearing rotatably supports a shaft in the engine, such as a rotor shaft. The bearing is, in turn, supported by a SFD. The SFD damps vibrations from the rotor by providing a constant flow of oil to an annular chamber surrounding the bearing. The oil film can be squeezed through one or more exit channels when the bearing moves from its central position as a result of rotor shaft eccentricity. SFDs are not ideal because they offer sub-optimal damping characteristics while still requiring oil and maintenance. Additionally, the use of SFDs requires tolerancing for positioning of the rotor shaft and bearings that can introduce variations in the center of rotation of the shaft, further reducing performance. Vibrations from the jet engine causing the eccentricity can propagate to the rest of the aircraft through the structure of the aircraft.